1. Field of the Invention
The present invention relates to a micro-fluidic oscillator and, more particularly, to a micro-fluidic oscillator having a sudden-expansion micro nozzle to conquer fluid viscous force due to increase of instability of fluid so as to generate a self oscillation phenomenon at slow flow.
2. Description of Related Art
A fluidic oscillator makes use of instability of the fluid itself to generate oscillation. Because of restrictions of physical parameters, general fluidic oscillators can only generate oscillation under some flow speeds. If the flow speed is too low, the fluidic oscillators cannot successfully generate oscillation. This will result in much limit in applications, especially in the applications of micro fluidic.
As shown in FIG. 1, U.S. Pat. No. 3,902,367 discloses a fluidic oscillator 2 , which comprises an oscillation chamber 4 with attachment walls 61 and 62 at two sides thereof, a fluid inlet 8, a fluid outlet 10, two feedback channels 12 and 14, and a flow splitter 16. As shown in FIG. 2, U.S. Pat. No. 4,610,162 discloses a fluidic oscillator 18, which comprises an oscillation chamber 20 with attachment walls 221 and 222 at two sides thereof, a fluid inlet 24, a fluid outlet 26, two feedback channels 28 and 30, and a fluid splitter 32. As shown in FIG. 3, U.S. Pat. No. 6,860,157 discloses a fluidic oscillator 34, which comprises an oscillation chamber 36 with attachment walls 381 and 382 at two sides thereof, a fluid inlet 40, a fluid outlet 42, two feedback channels 44 and 46, and two fluid splitters 48.
The above prior art fluidic oscillators 2, 18 and 34 can still successfully operate under ordinary millimeter or micrometer scales to generate oscillation. However, it is found that fluid will move in a mode of stable laminar flow in the micrometer-scaled micro channels of the miniaturized fluidic oscillators 2, 18 and 34 once the fluidic oscillators 2, 18 and 34 are miniaturized with the same ratio. That is, the viscous force of fluid in the micrometer-scaled micro channels will increase substantially so that the micro fluidic will be very stable and can hardly generate oscillation. Therefore, the fluidic oscillators cannot function normally. Although active micro elements can be integrated in the micro channels to perturb the micro fluidic in advance, the fabrication process of the active elements is cumbersome and they are subject to damage.
Accordingly, the present invention aims to propose a more perfect micro-fluidic oscillator to solve the above problems in the prior art.